1. Field of the Invention
The present invention relates to an imaging apparatus and an imaging method of a passive type applicable to an automatic focusing device being used for a digital camera, a silver salt camera and the other usual cameras.
2. Description of Related Art
Conventionally, there has been proposed a structure capable of measuring easily and accurately a distance to a subject having a shape including a various of contrast edges in an imaging apparatus having a passive type ranging device. The structure includes a plurality of arrays of photoelectric conversion elements disposed upward and downward respectively to a pair of images of the subject, a part for preparing image information for processing image information converted photo-electrically by a plurality of up and down array groups of the photoelectric conversion elements preparing image information in the same direction as a deviated direction in the same portions of the subject, and an image-deviation detecting part for detecting a deviated amount of optical images in the sane portions of the subject based on a pair of right and left image information prepared as described above (for reference, see Japanese Patent Laid-Open No. H8-334681).
In a ranging apparatus or imaging apparatus using fill-light radiating to a subject, there has been proposed a structure using a flash device for flash photograph as a source of fill-light to be capable of using flashing light as fill-light for an auto focus. In the structure, a camera controlling part determines that focus detection is not possible when a brightness of the subject or contrast is low as a result of measurement of light by a light measuring part, at this time, a built-in flash or exterior flash is emitted, and the light is used as the fill-light for an auto-focus ranging (for reference, see Japanese Patent Laid-Open No. H5-34577).
In a camera having an auto-focus (AF) adjusting device, if a difference of brightness between a subject and a background is large as in backlight or the like, there is possibility that erroneous focusing occurs by measuring the background. The erroneous focusing is not considered in Japanese Patent Laid-Open No. H8-334681 as described above.
On the other hand, in Japanese Patent Laid-Open No. H5-34577, if a subject has a low brightness or low contrast as a result of measurement of brightness of the subject, a strobe for flash photograph is emitted at the time of a ranging to use as fill-light when measuring a distance to the subject. However, if a brightness difference between the subject and a background is large, because the background has a high brightness, there is possibility that the fill-light is not emitted. In this way, the invention disclosed in the patent document has the same problem as in Japanese Patent Laid-Open No. H8-334681.
Causes of the problems in prior art as described above are that the ranging is impossible relating to areas corresponding to the low brightness of the subject, whereas, is possible relating to areas corresponding to the high brightness of the background, as a result, a ranging value in an area of the background is selected, therefore the erroneous focusing occurs. Consequently, there are requested measures to improve a state of low brightness of the subject by any methods, under circumstances generating the brightness difference between the subject and the background.
On the other hand, in a two step SW type release operation in a conventional auto-focusing camera, usually, a sequence is taken that AF (ranging), display of an AF result, and focusing are executed in a half-press (first step), and exposure, namely, shutter control is executed in a full-press (second step). In addition, in case of a camera with fill-light function, the fill-light is emitted simultaneously with an AF operation in the half-press of the release. However, if the fill-light is emitted simultaneously with the AF operation in the half-press of the release, if a subject photographed is a person, there is a problem that the person misunderstands that the photograph has been taken when emitting the fill-light in the half-press. In particular, this tendency is higher in case of using the strobe as the fill-light. Because the fill-light is emitted every the release is half-pressed in these cameras, there is a problem that an operating life of a battery becomes short and so on.
In addition, there have been known an auto-focus camera disclosed in Japanese Utility Model Laid-Open No. H7-22648 as a conventional art for driving a photographic lens in a position by measuring automatically a distance to a subject when operating a release or shutter, an illuminating device for photograph disclosed in Japanese Patent Laid-Open No. 2002-207236 as a conventional art for adjusting an emitted amount of light according to a distance to a subject, an auxiliary illuminating device for an auto-focusing camera disclosed in Japanese Patent No. 2691206 as a conventional art for carrying out a detection of focusing by radiation of light of the auxiliary illuminating device, and an auto-focusing camera disclosed in Japanese Patent No. 2709375 as a conventional auto-focusing camera having a flashing device projecting fill-light to a subject.